Fischer-Tropsch catalysts using multiple precursors

ABSTRACT

A method for making a catalyst is provided that features loading a catalytic metal to a support using at least two different precursor compounds of that said metal; and loading the promoter to the support in an amount effective so as to achieve similar promotion as for a comparable catalyst comprising a greater amount of the promoter using only one precursor compound, where the catalytic metal is selected from among Group 8 metals, 9 metal, Group 10 metals, and combinations thereof. The promoter is preferably boron, silver, a noble metal, or combination thereof. Also provided are catalysts made by the method and Fischer-Tropsch processes that include contacting synthesis gas with a catalyst made by the method.

CROSS-REFERENCE TO RELATED APPLICATIONS

Not Applicable.

STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH OR DEVELOPMENT

Not Applicable.

FIELD OF THE INVENTION

The present invention relates generally to a method for making acatalyst that includes loading a catalytic metal to a support where thecatalytic metal is in the form of at least two precursor compounds andloading a promoter to the support. More particularly, the presentinvention relates to a catalyst made by the above-described method andthe use thereof in a process for the production of hydrocarbons thatincludes contacting carbon monoxide and hydrogen with the catalyst.

BACKGROUND OF THE INVENTION

Natural gas, found in deposits in the earth, is an abundant energyresource. For example, natural gas commonly serves as a fuel forheating, cooking, and power generation, among other things. The processof obtaining natural gas from an earth formation typically includesdrilling a well into the formation. Wells that provide natural gas areoften remote from locations with a demand for the consumption of thenatural gas.

Thus, natural gas is conventionally transported large distances from thewellhead to commercial destinations in pipelines. This transportationpresents technological challenges due in part to the large volumeoccupied by a gas. Because the volume of a gas is so much greater thanthe volume of a liquid containing the same number of gas molecules, theprocess of transporting natural gas typically includes chilling and/orpressurizing the natural gas in order to liquefy it. However, thiscontributes to the final cost of the natural gas and is not economical.

Further, naturally occurring sources of crude oil used for liquid fuelssuch as gasoline and middle distillates have been decreasing andsupplies are not expected to meet demand in the coming years. Middledistillates typically include heating oil, jet fuel, diesel fuel, andkerosene. Fuels that are liquid under standard atmospheric conditionshave the advantage that in addition to their value, they can betransported more easily in a pipeline than natural gas, since they donot require energy, equipment, and expense required for liquefaction.

Thus, for all of the above-described reasons, there has been interest indeveloping technologies for converting natural gas to more readilytransportable liquid fuels, i.e. to fuels that are liquid at standardtemperatures and pressures. One method for converting natural gas toliquid fuels involves two sequential chemical transformations. In thefirst transformation, natural gas or methane, the major chemicalcomponent of natural gas, is reacted with oxygen to form syngas, whichis a combination of carbon monoxide gas and hydrogen gas. In the secondtransformation, known as the Fischer-Tropsch process, carbon monoxide isconverted into a mixture of carbon monoxide and hydrogen (i.e.,synthesis gas or syngas). Those organic molecules containing only carbonand hydrogen are known as hydrocarbons. In addition, other organicmolecules containing oxygen in addition to carbon and hydrogen known asoxygenates may be formed during the Fischer-Tropsch process.Hydrocarbons having carbons linked in a straight chain are known asaliphatic hydrocarbons that may include paraffins and/or olefins.Paraffins are particularly desirable as the basis of synthetic dieselfuel.

The Fischer-Tropsch process is commonly facilitated by a catalyst.Catalysts desirably have the function of increasing the rate of areaction without being consumed by the reaction. A feed containingcarbon monoxide and hydrogen is typically contacted with a catalyst in areactor. In a batch process, the reactor is closed to introduction ofnew feed and exit of products. In a continuous process, the reactor isopen, with an inflow containing feed, termed a feed stream, passed intothe reactor and an outflow containing product, termed a product stream,passed out of the reactor.

Typically the Fischer-Tropsch product stream contains hydrocarbonshaving a range of numbers of carbon atoms, and thus having a range ofmolecular weights. Thus, the Fischer-Tropsch products produced byconversion of natural gas commonly contain a range of hydrocarbonsincluding gases, liquids and waxes. Depending on the molecular weightproduct distribution, different Fischer-Tropsch product mixtures areideally suited to different uses. For example, Fischer-Tropsch productmixtures containing liquids may be processed to yield gasoline, as wellas heavier middle distillates. Hydrocarbon waxes may be subjected to anadditional processing step for conversion to liquid and/or gaseoushydrocarbons. Thus, in the production of a Fischer-Tropsch productstream for processing to a fuel it is desirable to obtain primarilyhydrocarbons that are liquids and waxes, that are nongaseoushydrocarbons (e.g. C₅₊ hydrocarbons).

Typically, in the Fischer-Tropsch synthesis, the product spectra can bedescribed by likening the Fischer-Tropsch reaction to a polymerizationreaction with a Shultz-Flory chain growth probability (α) that isindependent of the number of carbon atoms in the lengthening molecule. αis typically interpreted as the ratio of the mol fraction of the C_(n+1)product to the mol fraction of the C_(n) product. A value of α of atleast 0.72 is desirable for producing high carbon-length hydrocarbons,such as those of diesel fractions.

The composition of a catalyst influences the relative amounts ofhydrocarbons obtained from a Fischer-Tropsch catalytic process. Commoncatalysts for use in the Fischer-Tropsch process contain at least onemetal from Groups 8, 9, or 10 of the Periodic Table (in the new IUPACnotation, which is used throughout the present specification).

Cobalt metal is particularly desirable in catalysts used in convertingnatural gas to heavy hydrocarbons suitable for the production of dieselfuel. Alternatively, iron, nickel, and ruthenium have been used inFischer-Tropsch catalysts. Nickel catalysts favor termination and areuseful for aiding the selective production of methane from syngas. Ironhas the advantage of being readily available and relatively inexpensivebut the disadvantage of a water-gas shift activity. Ruthenium has theadvantage of high activity but is quite expensive. Consequently,although ruthenium is not the economically preferred catalyst forcommercial Fischer-Tropsch production, it is often used in lowconcentrations as a reduction promoter, particularly for cobalt basedFischer-Tropsch catalysts.

Catalysts often further employ a promoter in conjunction with theprincipal catalytic metal. A promoter typically improves a measure ofthe performance of a catalyst, such as productivity, lifetime,selectivity, reducibility, or regenerability. Further, in addition tothe catalytic metal, a Fischer-Tropsch catalyst often includes a supportmaterial. The support is typically a porous material that providesmechanical strength and a high surface area, in which the active metaland promoter(s) can be deposited. Catalyst supports for catalysts usedin Fischer-Tropsch synthesis of hydrocarbons have typically beenrefractory oxides (e.g., silica, alumina, titania, thoria, zirconia ormixtures thereof, such as silica-alumina). In particular, γ-alumina is apopular support for Fischer-Tropsch catalysts.

The method of preparation of a catalyst may influence the performance ofthe catalyst in the Fischer-Tropsch reaction. In a common method ofloading a Fischer-Tropsch metal to a support, the support is impregnatedwith a solution containing a dissolved metal-containing compound. Themetal may be impregnated in a single impregnation, drying andcalcinations step or in multiple steps. When a promoter is used, animpregnation solution may further contain a promoter-containingcompound. After drying the support, the resulting catalyst precursor iscalcined, typically by heating in an oxidizing atmosphere, to decomposethe metal-containing compound to a metal oxide. When the catalytic metalis cobalt, the catalyst precursor is then typically reduced in hydrogento convert the oxide compound to reduced “metallic” metal. When thecatalyst includes a promoter, the reduction conditions may causereduction of the promoter or the promoter may remain as an oxidecompound. Despite the vast knowledge of preparation techniques, there isongoing effort for improving methods of catalyst preparation.

Kraum and Baerns (Applied Catalyst A: General 1999, 186, p. 189)describe studies of the performance of titania-supported catalystsprepared with various cobalt compounds, including cobalt (III) acetylacetonate, cobalt acetate, cobalt oxalate, cobalt nitrate, andcobalt-EDTA. The nominal cobalt loading was 12 wt %. They concluded that“the type of cobalt precursor used for the preparation of TiO₂ supportedcatalysts affects activity and chain growth probability under fixed FTS[Fischer-Tropsch synthesis] conditions”. In particular, they concludedthat “For titania-supported catalysts, the use of oxalate, acetate andacetyl acetonate as cobalt precursors resulted in higher activitycompared with the reference catalyst prepared from nitrate.” However,the authors further concluded that “the range of chain growthprobabilities increased in the following order, cobalt (III) acetylacetonate (α=0.71)<cobalt acetate (α=0.74)<cobalt (II) acetyl acetonate,cobalt oxalate, cobalt nitrate, cobalt-EDTA (α=0.82-0.84).” The authorsfurther reported that “On adding 0.1 wt % Ru to the catalyst made fromcobalt (III) acetyl acetonate, α increased from 0.71 to 0.80.” Thusalthough the titania-supported catalysts prepared with cobalt acetateand cobalt (III) acetyl acetonate had higher activity, they were alsoless selective to heavier hydrocarbons.

Fan and Fujimoto. (Chemistry Letters 1999, p. 343) describe studies ofthe performance of silica supported catalysts prepared with variouscobalt compounds, including cobalt nitrate, cobalt acetate, cobaltchloride, and combinations of cobalt nitrate and cobalt acetate.Catalysts made by co-impregnating and sequentially impregnating cobaltnitrate and cobalt acetate were studied. The nominal cobalt loading was10 wt. %. The authors disclosed that ‘the order of catalytic activitywas Co (N/A)>Co (N+A), Co (A/N) and Co (N)>>Co (A).” where Co (N/A)indicates nitrate impregnated before acetate and Co (N+A) indicatesnitrate and acetate co-impregnated. Reported chain growth probabilitieswere similar for Co(N/A), Co (N+A), Co (A/N), and Co(N) (α=0.84-0.86).

A comparison of the results of Fan and Fujimoto with those of Kraum andBaerns suggests that the variation in catalyst performance with variouscobalt compounds is dependent on the nature of the support. Further, itis known that cobalt interacts more strongly with alumina than silica.Thus, there remains a need for an improved method of preparing asupported cobalt catalyst where the support includes alumina.

Further, it is well known that the use of noble metals improves theperformance of cobalt-based Fischer-Tropsch catalysts. However, the useof noble metal promoters has the disadvantage of increasing the cost ofFischer-Tropsch catalysts. Thus, there remains a need for a method ofmaking a cobalt-based Fischer-Tropsch catalyst that involves the use ofreduced amounts of noble metal promoters.

SUMMARY OF THE PREFERRED EMBODIMENTS

According to a preferred embodiment of the present invention, method formaking a catalyst features loading a catalytic metal to a support in asingle or multi-step impregnations, using at least two differentprecursors of that metal. The method may further include loading apromoter to the support in an amount effective so as to achieve similarpromotion as for a comparable catalyst comprising a greater amount ofthe promoter using just one precursor of that said catalyst metal.

The effective amount of promoter is preferably not more than 75%, morepreferably not more than 50% of the content of promoter in thecomparable catalyst.

It is preferred that one precursor is more easily reduced than theother(s), or that it produces an intermediate that is more easilyreduced than the other(s).

Each of the steps of loading of the cobalt as the first precursorcompound, loading of the cobalt as the second precursor compound, andloading the promoter may be carried out singly or in combination withany one or combination of the other steps and in any order.

A promoter preferably enhances the performance of the catalyst. Suitablemeasures of the performance that may be enhanced include selectivitytowards desired products, activity, stability, lifetime, reducibilityand resistance to potential poisoning by impurities such as sulfur,nitrogen, and oxygen-containing compounds. A promoter is preferably aFischer-Tropsch promoter, that is an element or compound that enhancesthe performance of a Fischer-Tropsch catalyst in a Fischer-Tropschprocess.

The catalytic metal is selected from among Group 8 metals, 9 metal,Group 10 metals, and combinations thereof, more preferably from amongcobalt, iron, and combinations thereof.

The promoter is preferably selected from the group consisting ofrhenium, ruthenium, platinum, palladium, rhodium, copper, silver, boron,potassium and gold.

The support preferably includes at least one metal oxide and may includeat least a second metal oxide. The support more preferably includes atleast 50% by weight alumina.

According to an alternative embodiment of the present invention, aprocess for the production of hydrocarbons features contacting carbonmonoxide and hydrogen with a catalyst so as to convert at least aportion of the carbon monoxide to the hydrocarbons, wherein the catalystis made by any of the above-described methods.

According to any one of the above-described embodiments the hydrocarbonsmay include diesel-range hydrocarbons. Alternatively, or in combination,the hydrocarbons may include waxes suitable for further processing intodiesel-range hydrocarbons. In some embodiments, the hydrocarbons may beselected from among liquid hydrocarbons, non-gaseous hydrocarbons,middle distillates, C₅₊ hydrocarbons, and C₁₁₊ hydrocarbons.

Thus, the preferred embodiments of the present invention comprise acombination of features and advantages which enable it to overcomevarious problems of prior catalysts and processes. The variouscharacteristics described above, as well as other features, will bereadily apparent to those skilled in the art upon reading the followingdetailed description of the preferred embodiments of the invention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

Catalyst Preparation

The present method of making a catalyst preferably includes loading aFischer-Tropsch metal using a single or multi-step impregnationtechnique, to a support as a first precursor compound and a secondprecursor compound, and loading a promoter to the support. TheFischer-Tropsch metal preferably includes cobalt. The support preferablyincludes alumina. The promoter is preferably at least one of rhenium,ruthenium, platinum, palladium, boron, silver, rhodium, gold, andcombinations thereof. The promoter may be added as one or morepromoter-containing precursor compounds, also termed herein promotercompounds. According to some embodiments, the promoter is a metal thatacts as a reduction promoter.

The second precursor compound may be loaded separately after the firstprecursor compound. Alternatively, the second precursor compound may beloaded concurrently with the first precursor compound.

At least one of the Fischer-Tropsch metal precursor compounds ispreferably more easily reduced than the other. Alternatively at leastone of the Fischer-Tropsch metal precursors produces an intermediatethat is more readily reduced than the other precursor(s). The moreeasily reduced precursor compound is preferably loaded to the supportbefore the less easily reduced precursor compound(s). Although wishingnot to be bound or limited by this particular theory, the applicantsbelieve that the improvement in reduction from the use of at least 2different precursors of the same active metal is a result of thehydrogen spillover effect, thus resulting in needing less precious metalpromoter to achieve similar catalyst performance.

Thus, the method preferably includes loading the promoter to the supportin an amount effective so as to achieve similar promotion, and thuscatalyst performance, as for a comparable catalyst comprising a greateramount of the promoter prepared by using only one catalytic metalprecursor. The effective amount of promoter is preferably not more than75%, more preferably not more than 50% of the content of promoter in thecomparable catalyst.

Each of the steps of loading of the cobalt as the first precursorcompound, loading of the cobalt as the second precursor compound, andloading the promoter may be carried out singly or in combination withany one or combination of the other steps and in any order.

Loading a metal to a support as a precursor compound may be accomplishedby impregnation of the support with a solution containing the precursorcompound. The precursor compound may be a metal salt. The solvent may bewater. Alternatively, the solvent may be an organic solvent, such asacetone, methanol, higher alcohols, hexane, benzene, and the like. Theimpregnation may be incipient wetness impregnation. Thus theimpregnation may include contacting the support with a solution having avolume just sufficient to fill the pores of the support. Further, theimpregnation may include slurrying the support into the solutioncontaining the precursor compound. Further it is understood that theimpregnation can be done using multiple steps, and that drying orcalcination are optionally done in between each impregnation step.Typically, when the impregnated support is dried, drying proceeds forfrom 0.5 to 24 hours at a pressure of 1 to 75 atm and a temperaturebetween 70° C. and 150° C. Further, typically, when the impregnatedsupport is calcined, calcination proceeds for from 0.5 to 24 hours at apressure of 1 to 75 atm and a temperature between 200° C. and 900° C.

A promoter may be loaded simultaneous with at least a portion of theFischer-Tropsch metal. Alternatively, a promoter may be loaded after anyFischer-Tropsch metal. Still alternatively, a promoter compound may beloaded before any Fischer-Tropsch metal. Still alternatively, a promotermay be loaded between different steps of loading any Fischer-Tropschmetal. It is noted that the preferred method for loading the promoter isincipient wetness impregnation of a precursor compound of the promoter,although other methods known in the art are also suitable for loading apromoter. Either water or organic solvents may be used according to thesolubility of the compound. The promoter precursor compound may be asalt. It is understood that the impregnation of the promoter precursorcompound can be done using multiple steps, and that drying orcalcination, as described above, are optionally done in between eachimpregnation step.

Suitable cobalt-containing precursor compounds include, for example,hydrated cobalt nitrate (e.g. cobalt nitrate hexahydrate), cobaltcarbonyl, cobalt acetate, cobalt acetylacetonate, cobalt oxalate, andthe like. Hydrated cobalt nitrate, cobalt carbonyl and cobalt acetateare exemplary of cobalt-containing precursor compounds soluble in water.Cobalt oxalate is soluble in acids or acidic solutions. Cobalt acetateand cobalt acetylacetonate are exemplary of cobalt-containing precursorcompounds soluble in organic solvents.

Suitable rhenium-containing precursor compounds soluble in water arepreferred and include, for example, perrhenic acid, ammonium perrhenate,rhenium pentacarbonyl chloride, rhenium carbonyl, and the like.

Suitable ruthenium-containing precursor compounds soluble in waterinclude for example ruthenium carbonyl, Ru(NH₃)₆.Cl₃,Ru(III)2,4-pentanedionoate, ruthenium nitrosyl nitrate, and the like.Water-soluble ruthenium-containing precursor compounds are preferred.

Suitable platinum-containing precursor compounds soluble in waterinclude, for example, Pt(NH₃)₄(NO₃)₂ and the like. Alternatively, theplatinum-containing precursor may be soluble in an organic solvent, suchas platinum acetyl acetonate soluble in acetone.

Suitable boron-containing precursor compounds soluble in water include,for example, boric acid, and the like. Alternatively, theboron-containing precursor may be soluble in an organic solvent.

Suitable silver-containing precursor compounds soluble in water include,for example, silver nitrate (AgNO₃) and the like. Alternatively, thesilver-containing precursor may be soluble in an organic solvent.

Suitable palladium-containing precursor compounds include palladiumnitrate (Pd(NO₃)₂) and the like. Suitable palladium-containing precursorcompounds soluble in an organic solvent include palladium dioxide(PdO₂), which is soluble in acetone, and the like.

Typically, at least a portion of the metal(s) of the catalytic metalcomponent of the catalysts of the present invention is present in areduced state (i.e., in the metallic state). Therefore, it is normallyadvantageous to activate the catalyst prior to use by a reductiontreatment, in the presence of hydrogen at an elevated temperature.Typically, the catalyst is treated with hydrogen at a temperature in therange of from about 75° C. to about 500° C., for about 0.5 to about 36hours at a pressure of about 1 to about 75 atm, more preferably of about1 to about 10 atm. Pure hydrogen may be used in the reduction treatment,as may a mixture of hydrogen and an inert gas such as nitrogen, or amixture of hydrogen and other gases as are known in the art, such aslight hydrocarbons, carbon monoxide and carbon dioxide. Reduction withpure hydrogen and reduction with a mixture of mainly hydrogen and carbonmonoxide are preferred. The amount of hydrogen may range from about 1%to about 100% by volume.

Catalyst

The present catalyst preferably includes a catalytic metal. Thecatalytic metal is preferably a Fischer-Tropsch catalytic metal. Inparticular, the catalytic metal is preferably selected from the amongthe Group 8 metals, such as iron (Fe), ruthenium (Ru), and osmium (Os),Group 9 metals, such as cobalt (Co), rhodium (Rh), and iridium (Ir),Group 10 elements, such as nickel (Ni), palladium (Pd), and platinum(Pt), and the metals molybdenum (Mo), rhenium (Re), and tungsten (W).The catalytic metal is more preferably selected from the iron-groupmetals (i.e. cobalt, iron, and nickel), and combinations thereof. Thecatalytic metal still more preferably is selected from among cobalt andiron. The catalyst preferably contains a catalytically effective amountof the catalytic metal. The amount of catalytic metal present in thecatalyst may vary widely.

When the catalytic metal is cobalt, the catalyst preferably includescobalt in an amount totaling from about 1% to about 50% by weight (asthe metal) of total catalyst composition (catalytic metal, support, andany optional promoters), more preferably from about 5% to about 40% byweight, still more preferably from about 10% to about 37% by weight. Itwill be understood that % indicates percent throughout the presentspecification.

It will be understood that, when the catalyst includes more than onesupported metal, the catalytic metal, as termed herein, is the primarysupported metal present in the catalyst. The primary supported metal ispreferably determined by weight, that is the primary supported metal ispreferably present in the greatest % by weight.

The catalytic metal contained by a catalyst according to a preferredembodiment of the present invention is preferably in a reduced, metallicstate before use of the catalyst in the Fischer-Tropsch synthesis.However, it will be understood that the catalytic metal may be presentin the form of a metal compound, such as a metal oxide, a metalhydroxide, and the like. The catalytic metal is preferably uniformlydispersed throughout a support. It is also understood that the catalyticmetal can be also present at the surface of the support, in particularon the surface or within a surface region of the support, or that thecatalytic metal can be non-homogeneously dispersed onto the support.

Suitable support materials include metal oxides, and combinationsthereof. For example, suitable support materials include but are notlimited to alumina, modified alumina, silica-alumina, titania, zirconia,fluorided metal oxides, borated alumina, aluminum fluoride, aluminumboride, and combinations thereof. Alumina or modified alumina arepreferred supports. Optionally, the present catalyst may also include atleast one promoter known to those skilled in the art. The promoter mayvary according to the catalytic metal. A promoter may be an element thatalso, in an active form, has catalytic activity, in the absence of thecatalytic metal, such as ruthenium. Such an element will be termedherein a promoter when it is present in the catalyst in a lesser wt. %than the catalytic metal.

A promoter preferably enhances the performance of the catalyst. Suitablemeasures of the performance that may be enhanced include selectivitytowards desired products, activity, stability, lifetime, reducibilityand resistance to potential poisoning by impurities such as sulfur,nitrogen, and oxygen-containing compounds. A promoter is preferably aFischer-Tropsch promoter, that is an element or compound that enhancesthe performance of a Fischer-Tropsch catalyst in a Fischer-Tropschprocess.

It will be understood that as contemplated herein, an enhancedperformance of a promoted catalyst may be calculated according to anysuitable method known to one of ordinary skill in the art. Inparticular, an enhanced performance may be given as a percent andcomputed as the ratio of the performance difference to the performanceof a reference catalyst. The performance difference is between theperformance of the promoted catalyst and the reference catalyst, wherethe reference catalyst is a similar corresponding catalyst having thenominally same amounts, e.g. by weight percent, of all components exceptthe promoter. It will further be understood that as contemplated herein,a performance may be measured in any suitable units. For example, whenthe performance is the productivity, the productivity may be measured ingrams product per hour per liter reactor volume, grams product per hourper kilogram catalyst, and the like.

Suitable promoters vary with the catalytic metal and may be selectedfrom Groups 1-15 of the Periodic Table of the Elements. A promoter maybe in elemental form. Alternatively, a promoter may be present in anoxide compound. Further, a promoter may be present in an alloycontaining the catalytic metal. Except as otherwise specified herein, apromoter is preferably present in an amount to provide a weight ratio ofelemental promoter: elemental catalytic metal of from about 0.00005:1 toabout 0.5:1, preferably, from about 0.0005:1 to about 0.1:1 (dry basis).

Further, by way of example and not limitation, when the catalytic metalis cobalt, suitable promoters include Group 1 elements such as potassium(K), lithium (Li), sodium (Na), and cesium (Cs), Group 2 elements suchas calcium (Ca), magnesium (Mg), strontium (Sr), and barium (Ba), Group3 elements such as scandium (Sc), yttrium (Y), and lanthanum (La), Group4 elements such as (titanium) (Ti), zirconium (Zr), and hafnium (Hf),Group 5 elements such as vanadium (V), niobium (Nb), and tantalum (Ta),Group 6 elements such as molybdenum (Mo) and tungsten (W), Group 7elements such as rhenium (Re) and manganese (Mn), Group 8 elements suchas ruthenium (Ru) and osmium (Os), Group 9 elements such as rhodium (Rh)and iridium (Ir), Group 10 elements such as platinum (Pt) and palladium(Pd), Group 11 elements such as silver (Ag) and copper (Cu), Group 12elements, such as zinc (Zn), cadmium (Cd), and mercury (Hg), Group 13elements, such as gallium (Ga), indium (In), thallium (Tl), and boron(B), Group 14 elements such as tin (Sn) and lead (Pb), and Group 15elements such as phosphorus (P), bismuth (Bi), and antimony (Sb). Whenthe catalytic metal is cobalt, the promoter is preferably selected fromamong rhenium, ruthenium, platinum, palladium, boron, silver, andcombinations thereof.

When the catalyst includes rhenium, the rhenium is preferably present inthe catalyst in an amount between about 0.001 and about 5% by weight,more preferably between about 0.01 and about 2% by weight, mostpreferably between about 0.2 and about 1% by weight.

When the catalyst includes ruthenium, the ruthenium is preferablypresent in the catalyst in an amount between about 0.0001 and about 5%by weight, more preferably between about 0.001 and about 1% by weight,most preferably between about 0.01 and about 1% by weight.

When the catalyst includes platinum, the platinum is preferably presentin the catalyst in an amount between about 0.00001 and about 5% byweight, more preferably between about 0.0001 and about 1% by weight, andmost preferably between about 0.0005 and 1% by weight.

When the catalyst includes palladium, the palladium is preferablypresent in the catalyst in an amount between about 0.001 and about 5% byweight, more preferably between about 0.01 and about 2% by weight, mostpreferably between about 0.2 and about 1% by weight.

When the catalyst includes silver, the catalyst preferably has a nominalcomposition including from about 0.05 to about 10 wt % silver, morepreferably from about 0.07 to about 7 wt % silver, still more preferablyfrom about 0.1 to about 5 wt % silver.

When the catalyst includes boron, the catalyst preferably has a nominalcomposition including from about 0.025 to about 2 wt % boron, morepreferably from about 0.05 to about 1.8 wt. % boron, still morepreferably from about 0.075 to about 1.5 wt % boron.

As used herein, a nominal composition is preferably a compositionspecified with respect to an active catalyst. The active catalyst may beeither fresh or regenerated. The nominal composition may be determinedby experimental elemental analysis of an active catalyst. Alternatively,the nominal composition may be determined by numerical analysis from theknown amounts of catalytic metal, promoter, and support used to make thecatalyst. It will be understood that the nominal composition asdetermined by these two methods will typically agree within conventionalaccuracy.

Further, as used herein, it will be understood that each of the ranges,such as of ratio or weight %, herein is inclusive of its lower and uppervalues.

Fischer-Tropsch Operation

A process for producing hydrocarbons preferably includes contacting afeed stream that includes carbon monoxide and hydrogen with the presentcatalyst. Alternatively or in combination, a process for producinghydrocarbons includes contacting a feed stream that includes carbonmonoxide and hydrogen with a catalyst in reaction zone so as to producehydrocarbons, where the catalyst is a catalyst made according to thepresent method.

The feed gas charged to the process for producing hydrocarbons includeshydrogen, or a hydrogen source, and carbon monoxide. H₂/CO mixturessuitable as a feedstock for conversion to hydrocarbons according to theprocess of this invention can be obtained from light hydrocarbons suchas methane by means of steam reforming, partial oxidation, or otherprocesses known in the art. Preferably the hydrogen is provided by freehydrogen, although some Fischer-Tropsch catalysts have sufficient watergas shift activity to convert some water and carbon monoxide to carbondioxide and hydrogen, for use in the Fischer-Tropsch process. It ispreferred that the molar ratio of hydrogen to carbon monoxide in thefeed be greater than 0.5:1 (e.g., from about 0.67 to 2.5). Preferably,when cobalt, nickel, and/or ruthenium catalysts are used, the feed gasstream contains hydrogen and carbon monoxide in a molar ratio of about1.6:1 to 2.3:1. Preferably, when iron catalysts are used the feed gasstream contains hydrogen and carbon monoxide in a molar ratio betweenabout 1.4:1 to 2.3:1. The feed gas may also contain carbon dioxide. Thefeed gas stream should contain a low concentration of compounds orelements that have a deleterious effect on the catalyst, such aspoisons. For example, the feed gas may need to be pretreated to ensurethat it contains low concentrations of sulfur or nitrogen compounds suchas hydrogen sulfide, ammonia, hydrogen cyanide and carbonyl sulfides.

The feed gas is contacted with the catalyst in a reaction zone.Mechanical arrangements of conventional design may be employed as thereaction zone including, for example, plugged flow, continuous stirredtank, fixed bed, fluidized bed, slurry bubble column, reactivedistillation column, or ebulliating bed reactors, among others, may beused. The size and physical form of the catalyst may vary, depending onthe reactor in which it is to be used. Plug flow, fluidized bed,reactive distillation, ebulliating bed, and continuous stirred tankreactors have been delineated in “Chemical Reaction Engineering,” byOctave Levenspiel, and are known in the art, as are slurry bubblecolumn. A suitable slurry bubble column is described, for example, inco-pending commonly assigned U.S. patent application Ser. No.10/193,357, hereby incorporated herein by reference.

When the reaction zone includes a slurry bubble column, the columnpreferably includes a three-phase slurry. Further, a process forproducing hydrocarbons by contacting a feed stream including carbonmonoxide and hydrogen with a catalyst in a slurry bubble column,preferably includes dispersing the particles of the catalyst in a liquidphase comprising the hydrocarbons so as to form a two-phase slurry; anddispersing the hydrogen and carbon monoxide in the two-phase slurry soas the form the three-phase slurry. Further, the slurry bubble columnpreferably includes a vertical reactor and dispersal preferably includesinjection and distribution in the bottom half of the reactor.Alternatively, dispersal may occur in any suitable alternative manner,such as by injection and distribution in the top half of the reactor.

The Fischer-Tropsch process is typically run in a continuous mode. Inthis mode, the gas hourly space velocity through the reaction zone mayrange from about 50 to about 10,000 hr⁻¹, preferably from about 300 hr⁻¹to about 2,000 hr⁻¹. The gas hourly space velocity is defined as thevolume of reactants per time per reactor bed volume. The reaction zonetemperature is typically in the range from about 160° C. to about 300°C. Preferably, the reaction zone is operated at conversion promotingconditions at temperatures from about 190° C. to about 260° C. Thereaction zone pressure is typically in the range of about 80 psig (653kPa) to about 1000 psig (6994 kPa), preferably from 160 psig (1204 kPa)to about 600 psig (4237 kPa).

The products resulting from the process will have a great range ofmolecular weights. Typically, the carbon number range of the producthydrocarbons will start at methane and continue to about 50 to 100carbons or more per molecule as measured by current analyticaltechniques. The process is particularly useful for making hydrocarbonshaving five or more carbon atoms especially when the above-referencedpreferred space velocity, temperature and pressure ranges are employed.

The wide range of hydrocarbons produced in the reaction zone willtypically afford liquid phase products at the reaction zone operatingconditions. Therefore the effluent stream of the reaction zone willoften be a mixed phase stream including liquid and vapor phase products.The effluent stream of the reaction zone may be cooled to condenseadditional amounts of hydrocarbons and passed into a vapor-liquidseparation zone separating the liquid and vapor phase products. Thevapor phase material may be passed into a second stage of cooling forrecovery of additional hydrocarbons. The liquid phase material from theinitial vapor-liquid separation zone together with any liquid from asubsequent separation zone may be fed into a fractionation column.Typically, a stripping column is employed first to remove lighthydrocarbons such as propane and butane. The remaining hydrocarbons maybe passed into a fractionation column where they are separated byboiling point range into products such as naphtha, kerosene and fueloils. Hydrocarbons recovered from the reaction zone and having a boilingpoint above that of the desired products may be passed into conventionalprocessing equipment such as a hydrocracking zone in order to reducetheir molecular weight down to desired products such as middledistillates and gasoline. The gas phase recovered from the reactor zoneeffluent stream after hydrocarbon recovery may be partially recycled ifit contains a sufficient quantity of hydrogen and/or carbon monoxide.

Without further elaboration, it is believed that one skilled in the artcan, using the description herein, utilize the present invention to itsfullest extent. The following exemplary embodiments are to be construedas illustrative, and not as constraining the scope of the presentinvention in any way whatsoever.

EXAMPLES Comparative Example A

This is a comparative example for Example 1. A cobalt catalyst with anominal composition of 20% cobalt, 0.02% platinum, and 0.5% boron wasmade by impregnating γ-alumina. The γ-alumina was obtained from Condeaas Puralox SCCa 5/150. The γ-alumina was impregnated with an aqueoussolution of cobalt nitrate (Co(NO)₃6H₂O), platinum (II) acetylacetonate,and boric acid using an appropriate quantity for incipient wetness in atwo step impregnation process. The resulting catalyst precursor wasdried in air at 120° C. for 8 hours and calcined in air at 240° C. forfour hours. After reduction at 400° C. for 16 hours using pure hydrogenat a gas flow rate of 700 cc/min in a fluidized bed, the catalyst wastested in a bench scale fixed bed reactor under conditions of 220° C.temperature, 350 psi pressure, and a feed rate of 6 NL/hr/g catalyst,with a feed having a hydrogen to carbon monoxide molar ratio of 2.Results of testing are shown in Table 1.

TABLE 1 Single Precursor Catalyst C₅₊ C₁ CO₂/CO Age (hrs) CO Conv. (%)(g/hr/kg-cat) (wt. %) (mole %) 24 60 588 8.7 0.5 56 59 572 9.2 0.5 76 58560 9.3 0.5

Example 1

A catalyst with a nominal composition of 20 wt. % cobalt and 0.01 wt. %platinum on γ-alumina was prepared. The γ-alumina was obtained fromCondea as Puralox SCCa 5/150. Half of the cobalt was loaded byimpregnating the support with a first solution containing cobaltnitrate. The resulting catalyst precursor was dried overnight at 90° C.,dried at 120° C. for an hour and ramped at 2° C./min to 300° C. andcalcined at 300° C. for 5 hours. The calcination was in air flowing at700 mL/min. The other half of the cobalt was loaded by impregnating thesupport with a second solution containing cobalt acetate. The secondsolution also contained platinum acetyl acetonate. The resultingcatalyst precursor was dried overnight at 90° C., dried at 120° C. foran hour and ramped at 2° C./min to 300° C. and calcined at 300° C. for 5hours. The calcination was in air flowing at 700 mL/min. After reductionat 400° C. for 16 hours using pure hydrogen at 700 mL/min in a fluidizedbed the catalyst was tested in a bench scale fixed bed reactor underconditions of 220° C. temperature, 350 psi pressure, and a feed rate of6 NL/hr/g-catalyst, with a feed having a hydrogen to carbon monoxidemolar ratio of 2. Results of testing are shown in Table 2.

TABLE 2 Multiple Precursors Catalyst CO Conv. C₅₊ C₁ CO₂/CO Age (hrs)(%) (g/hr/kg-cat) (wt. %) (mole %) 22.5 76 784 6.0 1.0 46.5 64 615 9.60.7 63 63 598 9.4 1.0

This example shows that a catalyst made with two precursors and promotedwith platinum (Example 1) performed as well as a comparable catalystpromoted with twice as much platinum (Example A). Comparable performancewas seen in each of the CO conversion, C₅₊ productivity, and C₁selectivity.

Should the disclosure of any of the patents and publications that areincorporated herein conflict with the present specification to theextent that it might render a term unclear, the present specificationshall take precedence.

While preferred embodiments of this invention have been shown anddescribed, modifications thereof can be made by one skilled in the artwithout departing from the spirit or teaching of this invention. Theembodiments described herein are exemplary only and are not limiting.Many variations and modifications of the catalyst and process arepossible and are within the scope of the invention. Accordingly, thescope of protection is not limited to the embodiments described herein,but is only limited by the claims that follow, the scope of which shallinclude all equivalents of the subject matter of the claims.

What is claimed is:
 1. A process for the production of hydrocarbonscomprising: contacting carbon monoxide and hydrogen with a synthesiscatalyst so as to convert at least a portion of the carbon monoxide tothe hydrocarbons, wherein the catalyst is made by a method comprising:(a) loading a Fischer-Tropsch metal to a porous support wherein theFischer-Tropsch metal is in the form of at least a first precursorcompound of the Fischer-Tropsch metal and a second precursor compound ofthe Fisher-Tropsch metal, wherein the first precursor compound and thesecond precursor compound are loaded separately; and (b) loading thepromoter to the support in an amount effective so as to achieve similarperformance of the catalyst as the performance of a comparable catalystcomprising a greater amount of the promoter and prepared by loading notmore than one of the precursor compounds of the metal.
 2. The processaccording to claim 1 wherein step (a) comprises selecting the precursorssuch that the portion of the metal loaded in the form of one of thefirst and second precursors is more easily reduced than the portion ofthe metal loaded in the form of the other of the first and secondprecursors.
 3. The process according to claim 1 wherein at least aportion of step (b) is simultaneous with at least a portion of step (a)such that at least a portion of the promoter is loaded concurrently withat least a portion of the Fischer-Tropsch metal.
 4. The processaccording to claim 1 wherein step (b) follows step (a).
 5. The processaccording to claim 1 wherein step (b) precedes step (a).
 6. The processaccording to claim 1 wherein the effective amount is not more than 75%of the content of promoter in the comparison catalyst.
 7. The processaccording to claim 1 wherein the effective amount is not more than 50%of the content of promoter in the comparison catalyst.
 8. The processaccording to claim 1 wherein the performance is selected from the groupconsisting of activity, stability, reducibility and selectivity.
 9. Theprocess according to claim 1 wherein the promoter is selected from thegroup consisting of rhenium, ruthenium, platinum, palladium, rhodium,copper, silver, rhodium, boron, gold, and combinations thereof.
 10. Theprocess according to claim 1 wherein the support is selected from thegroup consisting of alumina, modified alumina, silica-alumina, titania,zirconia, fluorided metal oxides, borated alumina, aluminum fluoride,aluminum boride, and combinations thereof.
 11. The process according toclaim 10 wherein the support is selected from the group consisting ofalumina, modified alumina, and combinations thereof.
 12. The processaccording to claim 11 wherein the support comprises at least 50% byweight alumina.
 13. The process according to claim 12 wherein thesupport further comprises a second metal oxide.
 14. The processaccording to claim 1 wherein the Fischer-Tropsch metal comprises cobalt.15. A process for the production of hydrocarbons comprising: contactingcarbon monoxide and hydrogen with a production catalyst so as to convertat least a portion of the carbon monoxide to the hydrocarbons, whereinthe catalyst comprises a support comprising at least 50% alumina,cobalt, and a noble metal; wherein the catalyst is made by a methodcomprising: (a) loading the cobalt to the support as a first precursorcompound and a second precursor compound, wherein the first precursorcompound and the second precursor compound are loaded separately; and(b) loading the noble metal to the support; and wherein the non-gaseoushydrocarbon yield is similar to that of a comparable catalyst comprisingcobalt and the noble metal, wherein the synthesis catalyst contains alesser amount of the noble metal than does the comparison catalyst. 16.The process according to claim 15 wherein step (a) comprises selectingthe precursors such that the portion of the metal loaded in the form ofone of the first and second precursors is more easily reduced than theportion of the metal loaded in the form of the other of the first andsecond precursors.
 17. The process according to claim 15 wherein saidcatalyst further comprises boron.
 18. The process according to claim 15wherein at least a portion of step (b) is simultaneous with at least aportion of step (a) such that at least a portion of the promoter isloaded concurrently with at least a portion of the Fischer-Tropschmetal.
 19. The process according to claim 15 wherein step (b) followsstep (a).
 20. The process according to claim 15 wherein step (b)precedes step (a).
 21. The process according to claim 15 wherein thelesser amount is not more than 75% of the content of promoter in thecomparison catalyst.
 22. The process according to claim 15 wherein thelesser amount is not more than 50% of the content of promoter in thecomparison catalyst.